Perforating into the rock matrix around a well bore is accomplished primarily by either shooting a bullet projectile into the rock matrix or detonating a shaped charge directed into the rock matrix, the latter being the most prevalent practice in perforating in recent times. While perforating wells by detonation of shaped charges into the rock structure has been widely used, quite highly developed, and has enjoyed a relatively high success, there are still many problems associated with perforating by means of shaped charges that have not heretofore been solved. For example, a typical perforation from a state-of-the-art shaped charge is in the form of a slender, conically shaped penetration of constantly decreasing cross-sectional area into the rock structure. Since formation damage commonly occurs to some extent around a well bore from the well drilling fluids, it is necessary that the perforation penetrate a sufficient distance into the rock structure to reach through the damaged area around the well bore to allow fluids in the formation to flow into the well. The depth of penetration of conventional while being sufficient in most cases, is not particularly great, and the shape of the conventional penetration is conical with a constantly decreasing diameter; therefore, it is usually only the extreme tip or distal end portion of the perforation where the diameter and cross-sectional area are very small that pentrates through the damaged portion of the rock into previously undisturbed formation structure. Consequently, the effective cross-sectional area of perforation through which well fluids can flow into the well is quite small.
Another problem caused by the shaped charge perforating itself is that the pressure and heat resulting from the penetration of the blast into the rock structure causes some fusion of the rock structure to occur resulting in an impervious shell immediately around the perforation. Consequently, even where the perforation reaches beyond the range of formation damage caused by invading well drilling fluids, the perforation process itself causes an impervious zone around each perforation for substantially its entire length, again leaving a relatively small effective cross-sectional area of conduit through which fluids can flow into the well. After a well has produced for a period of time, deposits of solid materials build up within the pores and flow conduit structures in the formation around the perforations and well bore. These deposits are commonly known as "gyp" or calcium carbonate and some varieties of iron sulfide, and they impede the flow of fluids into the well from the formation.
In some kinds of formations, further stimulation of the wells can be effective, such as, by acid treatment, i.e., pumping an acid such as hydrochloric acid or sulphuric acid or a mixture of both into the well, or hydraulically fracturing the rock formation in the well. These stimulation operations are not always successful due to formation materials that react adversely to the carrier fluids used in the stimulations or due to inability to initiate a fracture in the rock matrix at pressures that can be withstood by the well tubing or casing.